For what its worth, I have no use for Flash Hiders. I'm not in the military. I'd much rather have the muzzle stay planted. So I have brakes on all my guns. Even pre-ban ARs.
With that in mind, it is easy to get one of these:
http://www.kineti-tech.com/m-p-15-22-thread-adapter/
If is perfectly legal since the barrel is not threaded.
If you put a brake on this, you end up with the benefits of a brake and it looks "cool" to those to which it matters.
And before anyone says that you are a wimp if you need a brake on a .22, please realize that recoil, even minimal recoil slows you down when you are trying to do something like clear a plate rack as fast as possible. A brake on a .22 rifle can make a big difference.